Re: EXPLAIN and nfiltered

Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> writes:
> Here's a patch for showing in EXPLAIN ANALYZE the number of rows a plan
> qual filtered from a node's input.

I don't like this a whole lot. It's unclear what "filtered" means,
or why it's worth expending precious EXPLAIN ANALYZE output space for.

Also, you've not implemented it for any except scan nodes; and I
think it's not going to be entirely well-defined for join nodes,
since it's somewhat arbitrary which conditions are considered part
of the join qual versus the filter. (That problem will get worse
not better with the planned generalization of inner indexscans,
since there may be join quals in scan nodes.)

regards, tom lane